Study plots solar system's rapid timeline

Friday, 6 June 2014 Stuart GaryABC

New meteorite dating measurements confirm planets began forming within the first two million years of the the birth of the solar system (Source: NASA/ESA/Garlick space-art.co.uk/University of Warwick/University of Cambridge)

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Planetary dating The first planetary seeds may have begun forming as soon as 600,000 years after the birth of our solar system, according to a new study.

The new research led by Thomas Kruijer of the Westfalische Wilhelms University in Germany, and published in the journal Science, provides the clearest view yet of how and when the first planetesimals began to accrete and develop.

"Understanding core formation in meteorite parent bodies is critical for constraining the fundamental processes of protoplanet accretion and differentiation within the solar [planetesimals] disk," the authors write.

The solar system formed out of a molecular cloud about 4.6 billion years ago with a proto-planetary disk rotating around the early Sun. Eventually this cloud condensed to form planetesimals, which later grew to become planets and other solar system bodies.

Kruijer and colleagues used tungsten radioactive isotope dating to determine the ages of five types of iron meteorites, which are thought to have created the cores of planetesimals.

As these planetesimals grow, they heat up and melt due to the energy of the impacts and the decay of radioactive elements.

Heavier elements such as iron sink to the middle through a process called differentiation and eventually form the core.

Cosmic rays

By determining the age of the iron meteorites, scientists can determine when planets first began to form, and how long the process took.

Kruijer and colleagues overcame the contamination by using platinum isotope compositions to correct for the effects of the cosmic rays.

They found core formation in the parent bodies of iron meteorites occurred within 100,000 years to 300,000 years of the formation of the first solid material to condense in the solar system.

Planet building models

"The findings provide a better understanding of when planetesimals grew large enough to generate the heat needed to allow a core to form and build a planet," says Dr Jonti Horner of the University of Southern Queensland.

"This supports the core accretion model of planetary formation, in which you start with lots of rocks and ice, but nothing big, and the bits crash into each other and grow over time."

According to Horner, the previous model's major problem was that it took up to twenty million years for a core to form, while the material needed for the process would be blown away by the Sun in less than half that time.

"This study shows that you can accrete an object large enough to differentiate into a core, mantle and crust on very short time scales of just a million years."

The asteroid that slammed into Earth 66 million years ago accelerated volcanic eruptions in India creating a double-whammy disaster that wiped out the dinosaurs. Also; new insights into the dwarf planet Ceres, and neutrino discovery awarded the Nobel Prize in Physics.